I also miss a lot in Grille. Not to mention ghost shells and shells that hit the dirt when fully aimed... RNG hates Grille. Oh the worst part is hitting another Grille with HE for 300 dmg while he hits you back with 1000....

I have similar issues in the SU-122-54 when the cannon is near the left or right traverse limits. Might as well be a miss when it is anywhere near the sides, even if stationary and shots are patiently aimed in on target.